Our long-range goal is to understand how different regions of the brain select, plan, and implement skilled actions. In the current proposal, the focus is on hand choice; how people select one hand or the other to reach for and interact with objects in the environment. This problem is encountered many times each day-- picking up a coffee cup, using the telephone, pointing to a landmark when giving directions -- and accomplished in a seemingly effortless manner. However, the psychological processes and neural mechanisms engaged in solving this simple decision process have received minimal attention in the literature. Similar to findings in research on perceptual choices, our recent studies demonstrate that hand choice involves a competitive process between representations associated with the selection of the left or right hand. To date, our work has generally focused on behavior, characterizing the psychological and physiological processes involved in hand choice. In the proposed work, the emphasis will be on identifying cortical and subcortical regions associated with this elementary, yet fundamental decision process. To this end, three specific aims will be addressed. 1) Identify the neural regions involved in hand choice during unimanual actions. 2) Use a reinforcement learning task to directly compare processes involving in using feedback when the outcomes are associated with variation in the participant's sense of limb control. As a point of comparison here, the data from the hand choice task will be compared to a more standard decision-making task involving object choice. 3) Identify the neural regions associated with inhibitory processes involved in hand selection and response initiation. The experimental plan entails the integrated use of functional imaging, brain stimulation, and neuropsychological studies. At the completion of this project, we expect to have made significant advances, not only in our understanding of action selection, but also in how we control and inhibit actions. PUBLIC HEALTH RELEVANCE: The proposed experiments will identify the neural processes that underlie the simple decision to use the left or right hand when reaching for an object, a fundamental aspect of human behavior. Insights gained from this work should add to our understanding of a range of neurological disorders. These include stroke patients who frequently fail to use their contralesional limb, even after recovering the capability to use the limb, and individuals who exhibit aberrations in inhibitory control, given preliminary evidence tha this basic decision process entails the operation of two dissociable inhibitory processes engaged during action selection and preparation.